Synthesis of Triphenylphosphine oxide

20 g of triphenylphosphine is dissolved in 230 mL of 95% aq. ethanol while heating to 70°C, a slow addition with stirring of 400 g of 20% aq. solution (w/w) of Oxone® is then started while maintaining the temperature below 75°C. The stirring is continued for another 4 h at 70-75°C, then the ethanol is evaporated off from the solution and the mixture is diluted with 200 mL of water and cooled down. The mixture is filtered, washed with water and the residue is dried in open air. The crude product can be recrystallized from hot toluene, and then heated until molten to remove traces of toluene.